The present invention relates to a brush seal for sealing between static components of a turbine and particularly relates to a brush seal for sealing between an inlet and the inner web of a first stage nozzle to minimize leakage flows into the inlet packing ring region of a steam turbine.
Seals are oftentimes employed between static components of a turbine. For example, in a steam turbine, static seals are employed in the inlet region to minimize steam leakage flows into packing ring locations between the packing ring casing and the rotor and forming the high pressure end seals. The seals, for example, between the inlet and the inner web of the first stage nozzle have included a plurality of labyrinth seal teeth mounted on sealing ring segments which may be spring biased to engage and seal against the opposing component. The packing ring seals carrying the labyrinth teeth can be preloaded and oriented in either radially outward or radially inward directions, depending on which component of the inlet region the seals are mounted. While labyrinth seals have been effective for minimizing leakage flows in these high pressure regions, the static annular or cylindrical components may become out-of-round or distorted which can result in increased leakage flow from the high pressure region to the high pressure end seal packing ring region. Thermal distortion or creep of one or both of the components can cause an out-of-roundness and the creation of a gap between the tips of the labyrinth seal teeth and the surface that they are sealing against. Thus, as long as the labyrinth seal teeth and the component parts remain circular, the labyrinth teeth are effective to minimize leakage flows. However, if one or both of the sealing surfaces becomes out-of-round, a generally crescent-shaped gap is created between the tips of the teeth and the adjacent sealing surface, resulting in leakage across the seal through the gap and a performance loss. Any increased leakage past the labyrinth seal teeth decreases the effectiveness of the energetic fluid, e.g., steam, flowing along the flowpath of the turbine. Consequently, there is a need for a sealing arrangement between static components of a turbine which will accommodate distortion or out-of-roundness of the components to be sealed while maintaining an effective seal.
In a preferred embodiment according to the present invention, there is provided a static seal for a turbine, comprising first and second stationary turbine components having respective first and second surfaces in opposition to one another, at least one of the first components being subject to distortion, opening a gap between the first surface and the second surface and a brush seal carried by one of the first and second components having a plurality of bristles with an initial interference between tips of the bristles and another of the first and second components for compliant engagement with another of the first and second components maintaining the seal between the surfaces and across the gap.
In a further preferred embodiment according to the present invention, there is provided a steam path including a steam inlet and a first stage nozzle having an inner web, the inlet and inner web having respective first and second surfaces in generally radial opposition to one another, at least one of the inlet and the inner web being subject to distortion opening a gap between the first surface and said second surface and a brush seal carried by one of the inlet and the inner web having a plurality of bristles with an initial interference between tips of the bristles and another of the inlet and the inner web for compliant engagement with another of the inlet and the inner web maintaining a static seal between the surfaces and across the gap.